Update load-balancing.md with SSL binding gotcha

If you don't add http bindings to your IIS site, publish will not work in this configuration unless you set umbracoUseSSL="true" in your web.config. This is somewhat non-obvious, and given the technical level of this document, I think including this information here is appropriate.
Merge pull request #144 from pwn493/patch-1

Update load-balancing.md with SSL binding gotcha